The rehabilitation of Marc Brunel's Thames Tunnel was undertaken over a 24 month period by Atkins and Dr. G. Sauer Company Ltd. (DSC) acting as a specialist tunneling, shotcrete and waterproofing consultant, with the contract novated to Taylor Woodrow Civil Engineering Ltd. (TWCE).

The reconstruction of tunnels may afford the opportunity to significantly enlarge the tunnel dimensions.

The Port Authority of Allegheny County, Pittsburgh, Pennsylvania, is very pleased with its Berry Street Tunnel reconstruction results. The authority benefited from the contractor's original low bid and its post-bid tunnel-design change. The original bid was almost US$ 3 million lower than the nearest competitor, a fair proportion for a project costing under US$ 40 million.

Within the last 10 to 15 years, tunnel sealing (rehabilitation with cladding and installation of a waterproofing system) became a solid feature of tunneling in Europe. In other countries worldwide, e.g. U.S., Asia, etc., similar rehabilitation concepts have been applied since about 1985. A vast majority of older road tunnels show seriously damaged areas resulting from water leakage into the tunnel interior. A typical example is shown in Figure 1.

Leakage of tunnels can result in a hazardous impact on traffic due to: